My contractor removed wallpaper from a bedroom in preparation for repairing plaster and painting. The wallpaper has been in place for about 20 years. When he pulled the backing off, all 4 walls were covered in mold very evenly except right where the strips joined. There is no water source nearby and none of the other wallpapered rooms had that problem.
We are speculating that the paper hanger may have used some paste that had been opened and not resealed well allowing mold spores to develop. Has anyone come across this before? Any other ideas as to the cause?